Small molecule may stop infectious biofilms growing on medical implants

Modern medicine relies hugely on the ability to attach and implant devices to and in the human body to treat a wide range of diseases and conditions. However, a big problem with their use is the fact that they offer prime real estate for the colonization of bacteria into resilient and hard-to-treat "biofilms" that result in chronic infections and increased treatment costs. Now, a new study offers a possible solution in the form of a small molecule that blocks the ability of a particularly stubborn and common infectious bacterium to form biofilms.

The ability to form biofilms helps stubborn and hard-to-treat infections such as MRSA to spread in the body.

The researchers - including microbiologists from Trinity College Dublin in Ireland - report their findings in the journal PNAS.

Bacteria generally exist in two states: as individual cells (planktonic state) or as organized colonies that stick to surfaces and are held together by a slimy, extracellular matrix made of molecules that they excrete.

As biofilms, bacteria can adhere to any natural or manmade surface. For example they can be found on submerged surfaces in nonsterile water and cause enormous problems for the maintenance of ship hulls, oil pipelines, and drinking water supplies. They are also a big problem for the food industry.

Even if a sterile surface is submerged - whether into seawater or fresh water - it almost immediately begins to be covered with a bacterial biofilm. In fact, one of the first thorough studies of biofilms was carried out in an alpine stream.

Bacterial biofilms can develop on many surfaces in and on the body, such as in chronic wounds, on the skin, in the gut, and in dental plaque. They are also thought to contribute to pneumonia in cystic fibrosis patients.

Biofilms on medical devices pose huge challenge

Biofilms can also develop on the surfaces of devices that are inserted or implanted into the body, such as pacemakers, heart valves, catheters, breast implants, artificial joints, and even contact lenses.

Infections caused by biofilms are more challenging to treat than infections caused by planktonic cells; they are strongly resistant to antibiotics and immune attack, and their occurrence on biomedical surfaces is thought to be a leading cause of death worldwide.

Consequently, there is an urgent need for new methods to tackle biofilm infections in medicine.

The new study concerns the bacterium Staphylococcus aureus, which shows a remarkable ability to form biofilms that are difficult to eradicate - a big factor in helping MRSA infections to spread in the body and resist treatment.

Small molecule disrupts bonds that help to form biofilms

The researchers focused on bonding interactions that occur between certain proteins on the surfaces of the bacterial cells as they aggregate during biofilm formation.

In their paper, they note that there is growing evidence that these interactions contribute to biofilm formation, but the underlying mechanisms are not clear.

They found that one surface protein in particular played a dual role. The protein is called SdrC and it promotes adhesion between bacterial cells, as well as attachment of cells to surfaces.

Further investigation revealed that a small molecule ("derived from β-neurexin") can block the SdrC interactions between cells, effectively stopping it from recognizing other bacterial cells. It can also block interactions between bacterial cells and surfaces to prevent biofilm formation.

The team believes that the findings could lead to new therapies that prevent biofilms forming on medical implants and devices, and that also help the recovery of patients following surgery.

"This exciting breakthrough will inform the design of new, targeted approaches to prevent biofilm formation by staphylococci and reduce the incidence of medical device-related infection."

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